1. Field of the Invention
This present invention relates generally to the predicting the distribution uniformity of landscape irrigation sprinkler systems under conditions of actual use, and more particularly, to modeling Irrigation distribution under all possible sprinkler operational conditions on three-dimensional terrain In the presence of wind. From the irrigation distribution modeling results, the distribution and efficiency are predicted.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Modem irrigation systems are designed and operated with the objective of conserving water. The efficiency is the ratio of the amount of the water need by the plants to the amount of water delivered to a landscape. An effective Irrigation design and site operation maximizes the Irrigation efficiency.
Ideally, when an Irrigation system is designed, its efficiency would also be calculated. The design could then be adjusted to maximize the Irrigation efficiency, thus minimizing the water consumption. In practice, it is very difficult to predict the efficiency of an Irrigation system. Instead, the design of irrigation system is often attempted using general rules based on experience. For example, for a rectangular or triangular pattern, the design rule is to use head to head spacing. In this case, distance to the nearest head is the same as the throw distance. It is not always possible to arrange the sprinkler heads Into a regular pattern In this case the recommend spacing must be used along with ones best Judgment. The Irrigation designer usually does not make use of irrigation efficiency calculation.
As modifications to an irrigation system occur, it would be advantageous for the effect on irrigation efficiency to be considered first, but in practice, technicians working in the field have little capability to do this. Technicians usually do not make use of an irrigation efficiency calculation.
In principle, the method for computing irrigation uniformity and efficiency is rather simple. If the distribution for each sprinkler nozzle is known, then the total distribution is obtained by superposition. From the total distribution, the uniformity and efficiency is then calculated. To use this method, one must first obtain measured distribution data. Available test data, such the data provided by the Center for Irrigation Technology at California State University, Fresno, provides distribution data for sprinkler nozzles irrigating flat ground with no wind present. Given this type of data, the irrigation distribution and efficiency can be calculated given the sprinkler positions and primary operational variables. For each sprinkler, these are the range of arc and pressure. This method, however, is very limited in its applicability to real landscapes.
Although the principles behind the computation for irrigation uniformity efficiency are well known, these principles have received only limited application. At the present time, only two products make any use of these principles, and both of these are very limited in their application. One is SPACE PRO™, which is available through the Center for Irrigation Technology at California State University. The other is the irrigation analysis component of LANDLOGIC by Landlogic in Scattsdale, Az. LANDLOGIC is mostly a facility management software tool. Both SPACE PRO™ and LANDLOGIC can only be used on flat terrain and only at a pressure corresponding to the test data.
In reality, to calculate the irrigation efficiency accurately, many other variables must be accounted for. The most important of these is the effect of terrain topology. Sprinklers are often used to irrigate slopes and rolling hill sides. For sprinkler located on slopes, the sprinkler is tilted in the direction of the slope. Typically the tilt angle is chosen to be about one half of the angle corresponding to the slope. The head tilt causes distribution to become asymmetric. The water then falls on an irregular three-dimensional surface, producing additional asymmetry. For this case, a flat ground calculation is not appropriate because the result would be inaccurate. For a slope, not only does the water not fall on a level surface, the sprinkler is not in its vertical upright position as it would be for a flat ground test. Flat ground test data cannot be used to calculate the distribution on slopes, rolling hills, or any other no-flat terrain topology.
Another very signification factor is the effect of wind. Unless the average wind is lower than around 5 miles per hours, using the test data obtained under windless laboratory conditions is also not appropriate because again the predicted results would be inaccurate. The data obtained under windless conditions cannot be used to calculate the distribution when the wind speed exceeds around 5 miles per hour.
In addition to the effect of terrain topology and wind, there are other operational variables that are also important. For modern sprinklers the flow and throw distance can often be adjusted via a screw setting on the sprinkler head. Typically, the reason for using this adjustment is to keep water spray inside the intended irrigation area. For example, one does not wish to irrigate concrete areas such as sidewalks or to irrigate beyond the property line. While flow/throw adjustments are common and have a significant effect on irrigation distribution, data corresponding to the various sprinkler settings is seldom available.
Not only is each of the above described variables important, the combined effect of the various variables is not additive. For example, if one has test data for a 10 mph wind on flat ground, and additionally, one has test data for no wind for a 1:2 slope. One cannot then calculate the distribution for a 10 mph wind going easterly on a west facing 1:2 slopes.
The combined effect of pressure variation, flow/throw setting, head tilt, and wind, produces a very rich variety of Irrigation distributions. To obtain data for all these variables, and all combinations of variables would be unfeasible. It would not be cost effective to conduct all the necessary tests.
At present, irrigated systems for landscapes are designed and operated without the benefit of irrigation efficiency because the current available methods are too limited in their applicability. These are applicable to only the simple case of flat ground with no wind at selected pressures and with the flow/throw adjustment set to the standard position.
There is need for a versatile method to accurately predict landscape irrigation efficiency. Such a method should account for all operational and environmental variables. These are the pressure variation, range of arc operation, flow/throw adjustment, head tilt, terrain topology, and wind. A calculation method with this versatility would be usable to anyone with a need to calculate Irrigation efficiency. The benefit of this kind of calculation would be clearly evident to anyone skilled in the art of irrigation design and operation.
The starting point for any distribution calculation data is measured data. To account for the effects of terrain topology and Wind, three dimensional test data is required. For flat ground testing, it is common to measure the distribution every two feet. For three dimensional testing, it would seem obvious to simply set up water buckets on a two foot grid that is both horizontal and vertical. However, that approach would be impractical. Too many points would be required, and many of these would be difficult to reach from the test floor.
The pressure delivered to each sprinkler nozzle is usually not uniform throughout an irrigated landscape. The pressure variation is due to elevation variation and pressure loss to due to flow through the Irrigation system pipes and equipment. While it is possible to make the pressure more uniform by installing pressure regulating valves, it is very common for an Irrigated site to have unregulated valves. A hydraulic calculation can predict the pressure at each sprinkler. Test data is usually obtained for a few selected pressures with the flow/throw adjustment set to the standard position.
Typically, these pressures are multiples of 10 PSI. What is need is a reliable method to predict irrigation distribution for intermediate pressures and throw settings.
What is a needed is method whereby the three-dimensional distribution may be calculated from the minimal number of test points. In principle, the three-dimensional distribution with wind present could be measured outdoors. However, the wind direction and speed cannot be controlled, and thus, the results would be unrepeatable. What is needed for this case is an alternative method to determine the distribution for a specified wind condition.